Question

正如另一个question I had asked earlier我想我可能已经找到了我的问题，但我需要专家的眼睛。

我发现文件/net/ipv4/tcp_zero_copy.c导致内核编译失败。

我对C或C ++的了解很少，当我在C / C ++编辑器中查看该文件时，看起来相同的代码重复过来（我认为是4次）。

我的问题很简单;

这是否足以导致编译器出现问题？如果相同的代码在同一个文件中反复出现？

这是文件的源代码（从头到尾总共148行）;

/*
 *  Support routines for TCP zero copy transmit
 *
 *  Created by Vladislav Bolkhovitin
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      version 2 as published by the Free Software Foundation.
 */

#include <linux/skbuff.h>

net_get_page_callback_t net_get_page_callback __read_mostly;
EXPORT_SYMBOL(net_get_page_callback);

net_put_page_callback_t net_put_page_callback __read_mostly;
EXPORT_SYMBOL(net_put_page_callback);

/*
 * Caller of this function must ensure that at the moment when it's called
 * there are no pages in the system with net_priv field set to non-zero
 * value. Hence, this function, as well as net_get_page() and net_put_page(),
 * don't need any protection.
 */
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback,
    net_put_page_callback_t put_callback)
{
    int res = 0;

    if ((net_get_page_callback != NULL) && (get_callback != NULL) &&
        (net_get_page_callback != get_callback)) {
        res = -EBUSY;
        goto out;
    }

    if ((net_put_page_callback != NULL) && (put_callback != NULL) &&
        (net_put_page_callback != put_callback)) {
        res = -EBUSY;
        goto out;
    }

    net_get_page_callback = get_callback;
    net_put_page_callback = put_callback;

out:
    return res;
}
EXPORT_SYMBOL(net_set_get_put_page_callbacks);
/*
 *  Support routines for TCP zero copy transmit
 *
 *  Created by Vladislav Bolkhovitin
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      version 2 as published by the Free Software Foundation.
 */

#include <linux/skbuff.h>

net_get_page_callback_t net_get_page_callback __read_mostly;
EXPORT_SYMBOL(net_get_page_callback);

net_put_page_callback_t net_put_page_callback __read_mostly;
EXPORT_SYMBOL(net_put_page_callback);

/*
 * Caller of this function must ensure that at the moment when it's called
 * there are no pages in the system with net_priv field set to non-zero
 * value. Hence, this function, as well as net_get_page() and net_put_page(),
 * don't need any protection.
 */
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback,
    net_put_page_callback_t put_callback)
{
    int res = 0;

    if ((net_get_page_callback != NULL) && (get_callback != NULL) &&
        (net_get_page_callback != get_callback)) {
        res = -EBUSY;
        goto out;
    }

    if ((net_put_page_callback != NULL) && (put_callback != NULL) &&
        (net_put_page_callback != put_callback)) {
        res = -EBUSY;
        goto out;
    }

    net_get_page_callback = get_callback;
    net_put_page_callback = put_callback;

out:
    return res;
}
EXPORT_SYMBOL(net_set_get_put_page_callbacks);
/*
 *  Support routines for TCP zero copy transmit
 *
 *  Created by Vladislav Bolkhovitin
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      version 2 as published by the Free Software Foundation.
 */

#include <linux/skbuff.h>

net_get_page_callback_t net_get_page_callback __read_mostly;
EXPORT_SYMBOL(net_get_page_callback);

net_put_page_callback_t net_put_page_callback __read_mostly;
EXPORT_SYMBOL(net_put_page_callback);

/*
 * Caller of this function must ensure that at the moment when it's called
 * there are no pages in the system with net_priv field set to non-zero
 * value. Hence, this function, as well as net_get_page() and net_put_page(),
 * don't need any protection.
 */
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback,
    net_put_page_callback_t put_callback)
{
    int res = 0;

    if ((net_get_page_callback != NULL) && (get_callback != NULL) &&
        (net_get_page_callback != get_callback)) {
        res = -EBUSY;
        goto out;
    }

    if ((net_put_page_callback != NULL) && (put_callback != NULL) &&
        (net_put_page_callback != put_callback)) {
        res = -EBUSY;
        goto out;
    }

    net_get_page_callback = get_callback;
    net_put_page_callback = put_callback;

out:
    return res;
}
EXPORT_SYMBOL(net_set_get_put_page_callbacks);

**编辑**

此外，我只是使用Notepad ++来比较它们看起来结束的各个代码块。根据比较工具，所有3个区块相互匹配。

这是编译器输出从死亡的地方返回给我的命令提示符。

  CC      net/ipv4/tcp_zero_copy.o
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__kcrctab_net_get_page_callbackâ
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__kcrctab_net_get_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__kstrtab_net_get_page_callbackâ
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__kstrtab_net_get_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__ksymtab_net_get_page_callbackâ
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__ksymtab_net_get_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__kcrctab_net_put_page_callbackâ
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__kcrctab_net_put_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__kstrtab_net_put_page_callbackâ
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__kstrtab_net_put_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__ksymtab_net_put_page_callbackâ
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__ksymtab_net_put_page_callbackâ was here
net/ipv4/tcp_zero_copy.c:74:5: error: redefinition of ânet_set_get_put_page_callbacksâ
net/ipv4/tcp_zero_copy.c:25:5: note: previous definition of ânet_set_get_put_page_callbacksâ was here
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__kcrctab_net_set_get_put_page_callbacksâ
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__kcrctab_net_set_get_put_page_callbacksâ was here
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__kstrtab_net_set_get_put_page_callbacksâ
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__kstrtab_net_set_get_put_page_callbacksâ was here
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__ksymtab_net_set_get_put_page_callbacksâ
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__ksymtab_net_set_get_put_page_callbacksâ was here
make[2]: *** [net/ipv4/tcp_zero_copy.o] Error 1
make[1]: *** [net/ipv4] Error 2
make: *** [net] Error 2
root@dev01:/usr/src/linux# ls

Answer 1

这取决于重复的内容，

重复的函数声明不会出现任何错误重复的函数定义会产生错误使用相同名称创建或定义的变量会产生错误。

#2＆amp; #3在破坏ODR（一个定义规则）时会出错。

void doSomething(); //no error
void doSomething();
void doSomething();

void doSomething()
{

}

int main()
{
    int i; //error
    int i;
    doSomething();
    return 1;
}

在此代码中：

net_get_page_callback_t net_get_page_callback __read_mostly;

定义一个变量并重复这样做，导致同一命名变量的多重定义，从而导致重定义错误。

Answer 2

在翻译单元中对函数进行多重定义是错误的。这就是这里发生的事情。尝试从编译中发布前几条错误消息。

可以重复导致编译错误的C源代码吗？

2 个答案: